This invention relates to internal combustion engines, and more particularly to a breather apparatus for such engines that relieves air pressure in the engine crankcase.
During the operation of an internal combustion engine, pressure develops within the crankcase--the compartment which contains both a lubricating fluid and air. Unless this pressure is relieved so that a partial vacuum is maintained in the crankcase, the lubricating fluid--typically oil--tends to leak through various seals and orifices in the engine compartment, resulting in engine malfunction. More specifically, the pressurized oil tends to flow into the intake of the engine's air cleaner, rendering the air cleaner unusable. Therefore, it is desirable to relieve the crankcase pressure that builds up due to engine operation by providing an escape for pressurized crankcase air.
Several breather techniques are known for relieving this engine crankcase pressure. Many of these breather techniques use complicated snap valves, duct valves, rubber valves, and one-way valves to relieve crankcase pressure without permitting the lubricating fluid from leaving the engine crankcase. Such prior art breathers contain an unnecessary number of parts, are unduly complicated, and expensive.
When the engine is a small engine used on lawnmowers, another problem occurs with prior art breather mechanisms. Lawnmower operators typically tip or rotate the lawnmower--and thus the engine--to one side or to the other for cleaning the underside of the lawnmower housing and the rotating blade. When the lawnmower engine is tipped, the engine's lubricating fluid may submerge the breather passageways, preventing crankcase pressure from being released. As discussed above, the unreleased crankcase pressure may then cause the crankcase lubricating fluid to leak through the seals or orifices in the engine compartment, resulting in engine or air cleaner malfunction.
It is therefore desirable to provide an engine breather mechanism that permits crankcase air pressure to be released even if the engine is rotated during cleaning.